Centre Henson's first game in Wales colours since the 2009 RBS 6 Nations Championship ended with him being substituted 20 minutes from time, and he could only look on as full-back Isa Nacewa's second try at the ground where he helped Leinster win the Heineken Cup just two weeks ago denied Wales victory.
Fly-half Brock James converted with the game's final kick, and Wales could only reflect on a poor overall performance in an error-strewn encounter.
Henson's most notable contribution was to create an early try for wing George North, and although he had few other opportunities the 29-year-old should still have done enough to be part of Wales' World Cup training squad.
North, his fellow wing Aled Brew, full-back Morgan Stoddart and scrum-half Mike Phillips scored Wales' tries, while Stephen Jones marked his 100th cap - only the second Welshman to achieve that feat after Gareth Thomas - by kicking all four conversions.
But the Barbarians, five points up at half-time, would not go away.
Nacewa (two), lock Joe Tekori, skipper Sergio Parisse and centre Mathieu Bastareaud claimed touchdowns, with Nacewa striking from long range as he capitalised on weak Welsh defence during the closing seconds.
Henson, after a combined total of just seven appearances for Saracens and Toulon in 26 months, was predictably more solid than spectacular.
He must now wait to see if his dream of playing in a first World Cup will gather momentum or fizzle out as Wales coach Warren Gatland ponders his options leading towards the 30-man squad cut-off date of August 22.
Henson says he has no regrets about his long self-imposed exile from rugby, and he will hope for further chances against Wales' World Cup warm-up opponents England (home and away) and Argentina in August.
Number eight Toby Faletau and prop Ryan Bevington benefited from the Welsh Rugby Union's contentious decision to award caps against a non-Test team, making their international debuts, while Cardiff Blues flanker Sam Warburton led Wales for the first time.
But Wales were without several injured or rested players - including Shane Williams, Lee Byrne, Jamie Roberts and Matthew Rees - while James Hook was getting married.
Warburton found himself opposing his Blues and Wales back-row colleague Martyn Williams, with Scarlets prop Iestyn Thomas also lining up in a Barbarians side that featured players from eight different countries.
Conditions were perfect for a running rugby spectacle under the stadium's open roof as Jones marked his cap century by leading Wales out.
The Barbarians dominated through a succession of early scrums, with Carl Hayman putting Bevington under pressure, but Wales scored from their first attack.
Phillips rifled possession wide and Henson delivered a telling pass - albeit one that looked forward - for the powerful North to finish off.
But Phillips then unwittingly set up the Barbarians' equalising try, seeing his pass intercepted by James before outstanding flanker Joe van Niekerk found Tekori with an exquisite offload that completed a 60-metre breakaway.
Wales received another piercing wake-up call just five minutes later after Barbarians scrum-half Sebastien Tillous-Borde shredded the home defence far too easily and floated a long ball to the unmarked Nacewa.
Wales needed a swift, telling response, and it duly arrived courtesy of Stoddart when he intercepted Baa-baas lock Paul Tito's pass 65 metres out and outpaced his pursuers.
Jones' second successful conversion nudged Wales 14-12 ahead, but the Barbarians shaded a disappointing first half when Parisse powered over from a close-range scrum following a shambolic Welsh defensive lineout.
James' conversion made it 19-14 at the break, giving Gatland plenty of food for thought following 40 minutes that provided him with more questions than answers.
Wales' woes continued early in the second period when Brew was sin-binned by referee Alain Rolland for a high tackle on Paul Sackey.
But despite being temporarily down to 14 men, Wales struck when Brew was still off the pitch as Phillips burrowed his way over for a try that Jones improved.
Gatland predictably made a raft of changes early in the final quarter - his switches included first caps for prop Scott Andrews and hooker Lloyd Burns - and Brew's 65th-minute touchdown looked to have settled the contest until Nacewa's last-gasp clincher.
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The entire All Blacks apparel line has been updated for 2013/14. Check out the New Zealand All Blacks polo.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Gilbert Blitz 8S rugby cleat is a great cleat at a great price of $69.99. Get a new pair of cleats today.
A cool looking all black rugby cleat with the high performance adidas is known for. Get in the Gear!
Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
The All Blacks Performance t-shirt is black with hints of blue from the training jersey. Very Cool.
The New Zealand All Blacks training jersey for 2013/14. Get in the Gear!
The USA Rugby Pro Alternate rugby jersey is perfect for any fan of the Eagles. Get yours to wear during the summer Test matches.
The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.